Electrically-Responsive Hydrogels

ABSTRACT

Implants comprising electrically-responsive hydrogel are described. Systems to provide electricity to induce response in hydrogel-containing implants are described. Methods for utilizing said system and methods for utilizing said hydrogel-containing implants are described.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/549,514 filed Nov. 20, 2014 entitledElectrically-Responsive Hydrogels, which claims benefit of U.S.Provisional Application Ser. No. 61/919,637 filed Dec. 20, 2013 entitledElectrically-Responsive Hydrogels, which is hereby incorporated hereinby reference in its entirety.

BACKGROUND OF THE INVENTION

Vessel occlusion is often necessary in a variety of cases including butnot limited to treatment of aneurysms, atrial septal defects, patentforamen ovale, left atrial appendage occlusion, patent ductusarteriosis, fistula, arterio-venous malformations, fallopian tubeocclusion for the purposes of sterilization, and occlusion in theperipheral vasculature. One method of treatment involves insertion of anexpansile material, such as hydrogel, for occlusion. Hydrogel is anexpansile, hydrophilic polymer. Hydrogel can be incorporated inembolization coils or can be injected independently. Hydrogel typicallyexpands when exposed to material, such as blood. This response is basedon the pH of the material the hydrogel is exposed to. The hydrogel orhydrogel-containing implant has a contracted form during deployment, andadopts an expanded form suitable for occlusive purposes after exposureto blood. During interventional procedures, the working time forintroducing and deploying hydrogel or a hydrogel-containing implant isrelatively low due to its expansile properties. A method of controllinghydrogel expansion would thus be beneficial to extend working timeduring interventional procedures. Alternatively, a method of augmentinghydrogel expansion would be beneficial to enhance the space fillingproperties of the hydrogel or hydrogel-containing implant.

Broadly, a system and/or method to control contraction and/or expansionof a hydrogel could aid in interventional procedures.

SUMMARY OF THE INVENTION

In one embodiment an implant utilizing an electrically-responsivehydrogel is described.

In another embodiment a system used to control anelectrically-responsive hydrogel is described.

In another embodiment a method of controlling an electrically-responsivehydrogel is described.

In another embodiment a method of utilizing an electrically-responsivehydrogel is described.

In another embodiment a method of utilizing an implant comprising anelectrically-responsive hydrogel is described.

In another embodiment a drug delivery device utilizing anelectrically-responsive hydrogel is described.

In another embodiment a steerable catheter utilizing anelectrically-responsive hydrogel is described.

In another embodiment a liquid embolic delivery catheter utilizing anelectrically-responsive hydrogel is described.

In another embodiment an intrasaccular occlusion device utilizing anelectrically-responsive hydrogel is described.

In another embodiment a stroke treatment device utilizing anelectrically-responsive hydrogel is described.

In another embodiment an anchor utilizing an electrically-responsivehydrogel is described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an implant utilizing a hydrogel where said implant isin a contracted state.

FIG. 2 illustrates an implant utilizing a hydrogel where said implant isin an expanded state.

FIGS. 3-5 illustrate an implant utilizing a hydrogel, where said implantprogresses from a contracted through an expanded state.

FIG. 6 illustrates a system used to mitigate expansion of hydrogel in animplant.

FIG. 7 illustrates a system used to augment expansion of hydrogel in animplant.

FIG. 8 illustrates a system used to selectively either mitigate oraugment expansion of hydrogel in an implant.

FIGS. 9, 9 a, 9 b illustrate a system used to selectively eithermitigate or augment expansion of hydrogel in an implant, where saidsystem utilizes one voltage source.

FIG. 10 illustrates the junction of the core wire andhydrogel-containing implant.

FIGS. 11, 11 a-11 c illustrates a system used to both a) selectivelyeither mitigate or augment expansion of hydrogel in an implant and b)detach the hydrogel-containing implant.

DESCRIPTION OF EMBODIMENTS

Hydrogels may expand or contract based on electric impulse, see Collapseof Gels in an Electric Field, Science Vol. 218 pgs 467-469, Flow controlwith hydrogels, Advanced Drug Delivery Reviews 56 (2004) 199-210,Electro-responsive drug delivery from hydrogels, Journal of ControlledRelease 92 (2003) 1-7 all of which are hereby incorporated by referencein their entirety.

Generally, hydrogels used for interventional procedures (e.g., fillinganeurysms) expand on contact with blood.

A sufficiently high positive charge applied to a hydrogel results in oneof two scenarios. In one scenario the hydrogel will shrink or contract.In another scenario the hydrogel either will not expand or will notexpand as much as it would otherwise expand when exposed to blood oranother material of a comparable pH level. That is, the hydrogel will beprone to expand when exposed to blood, yet the contracting actionprovided by the positive charge will cause the hydrogel to expand lessthan it would otherwise.

During interventional procedures, procedure time is important since alengthy procedure time may result in expansion of the hydrogel, makingdeployment of the hydrogel or hydrogel-containing implant difficult. Forexample, if blood enters the delivery device (e.g., catheter) that thehydrogel or hydrogel-containing implant is delivered through the bloodmay react with the hydrogel causing expansion of the hydrogel andresulting in increased friction when pushing the hydrogel orhydrogel-containing implant through the delivery device. A positivecharge applied to the hydrogel during deployment would either shrink thehydrogel or mitigate expansion of the hydrogel when exposed to bloodduring deployment, thus increasing workable interventional proceduretimes.

Contrarily, a sufficiently high negative charge applied to a hydrogeltends to cause the hydrogel to expand or bulge. This property can beused to further enhance the space filling potential of a hydrogel orhydrogel-containing implant.

Please note for reference of the description provided the terms“proximal” and “distal” will generally be used relative to the positionof the implant within the vasculature. Thus the term “distal” will referto a more downstream facing position whereas the term “proximal” willrefer to a more upstream facing position. In this context, utilizingFIG. 1 as an example, tip 4 sits distal of coupler 13. Referring to FIG.10 as another example, core wire 28 sits proximal relative to implant 11and implant 11 sits distal relative to core wire 28.

FIG. 1 illustrates an implant 11 comprising a carrier 2 and hydrogel 1disposed within a lumen 3 of the carrier 2. Carrier 2 contains at leastone gap 7. The carrier, as an example, could be a helically wound coilcomprised of a metallic or polymeric material. Carrier 2 has a thickness8 and a diameter 9. Diameter 9 is shown in FIGS. 3-5. A tip 4 may beformed at the distal end of implant 11 by, for example, a laser, solder,adhesive, or melting the hydrogel material itself. Alternatively the tipcould be the same material as the carrier. A coupler 13 sits at theproximal end of implant 11 and is connected to a delivery system. In oneexample a degradable electrolytic, thermal, or mechanical linkage isconnected to coupler 13 to sever implant 11 from the delivery system. Inanother example coupler 13 is itself degradable by electrolytic,thermal, or mechanical means to sever implant 11 from the deliverysystem. One such thermal detachment system that could be used is shownin U.S. Pat. No. 8,182,506 and U.S. Publication No. 2006/0200192, whichare hereby incorporated by reference in their entirety. Anotherdetachment system that could be used is shown in U.S. Pat. No.6,620,152, which is hereby incorporated by reference in its entirety.

FIG. 1 is offered as an example configuration for a hydrogel-containingimplant. Other configurations could utilize hydrogel coating on theoutside of a coil or carrier member, hydrogel placed within a slottedtube/carrier member, hydrogel alone, or other possible configurations.

FIG. 2 illustrates implant 11 from FIG. 1 with hydrogel 1 expanded. Insome implant configurations the hydrogel may expand beyond carrierdiameter 9 through gap 7, as shown in FIG. 2. Alternatively, in otherimplant configurations the hydrogel may expand to the periphery carrierdiameter 9 or to a point within the periphery of carrier diameter 9. Theexpansile properties of the hydrogel, carrier diameter, carrier width,and tensile properties of the constituent carrier material are allproperties which can affect the amount of hydrogel expansion relative tothe carrier.

Hydrogel utilized for intravascular therapeutic applications (e.g.,filling an aneurysm) is typically designed to expand when exposed toblood to enhance space filling potential of the implant. If blood entersthe catheter and reacts with the hydrogel, the hydrogel may expandprematurely making tracking of the hydrogel-containing implant throughthe catheter or delivery device difficult. This is especially true forthe implant shown in FIGS. 1-2, where hydrogel 1 can expand beyondcarrier diameter 9. In another scenario, when placing thehydrogel-containing implant in the target treatment site, it may bedesirable to move the implant around prior to the hydrogel expanding tomake sure the implant is in the correct location within the treatmentsite. The natural expansion of hydrogel upon contact with blood limitsthe time available to do so.

Another implant configuration could utilize hydrogel placed within acarrier with a tighter winding (i.e. a smaller gap 7) than what is shownin FIG. 1. In such a configuration the hydrogel would expand and push onthe carrier, thus expanding the diameter of the carrier. As a result thehydrogel may not necessarily expand through the lumen of the carrier asshown in FIG. 2. Instead as the hydrogel expands it would push on thecarrier, resulting in the radial expansion of the carrier. Anotherimplant configuration could utilize a greater carrier thickness 8. Thethicker carrier would limit the ability of hydrogel to seep through thelumen of the carrier as the hydrogel expands and thus utilize theexpansion of the hydrogel to, in turn, assist the radial expansion ofthe carrier. In one example the carrier is heat-set to an initial shape.The hydrogel is affixed within the carrier and is stretched intotension. The stretching of the hydrogel causes the carrier to alsostretch. The diameter of the carrier windings effectively decreases asthe carrier stretches. When the hydrogel is exposed to blood and expandsthe hydrogel will, in turn, push on the carrier. This causes the carrierto radially expand and assume a shape closer to its initial,pre-tensioned diameter. This is shown in FIGS. 3-5.

FIG. 3 shows the initial shape of carrier 2. In FIG. 4 hydrogel 1 issecured to carrier 2 and put in tension, causing carrier 2 to alsostretch, thus decreasing diameter 9. In FIG. 5 hydrogel 1 swells due tocontact with blood, causing an expansion in diameter 9.

The tendency of hydrogel to contract upon exposure to a positive chargeand expand upon exposure to a negative charge can be useful for avariety of purposes. In a scenario described earlier, blood may enterthe delivery device causing premature expansion of the hydrogel duringdelivery of the hydrogel-containing implant. Applying an appropriatelysignificant positive charge to the hydrogel will shrink the hydrogel orlimit its expansion upon contact with blood, thus allowing easiermovement of the hydrogel-containing implant through the delivery device.The principle described above (applying an appropriately significantpositive charge to the hydrogel thus limiting its expansion) will alsohelp in a scenario described earlier involving placement of ahydrogel-containing implant within the vasculature. An appropriatelysignificant positive charge can be applied to the hydrogel to limit itsexpansion upon contact with blood. Once the implant is placedappropriately, the positive charge can be removed allowing the hydrogelto expand and fill the region. Alternatively, once the implant is placedappropriately a negative charge can be applied to the hydrogel toaugment its expansion, further enhancing the space filling capability ofthe hydrogel and/or hydrogel-containing implant.

FIG. 6 illustrates a system 20 to mitigate hydrogel expansion. Thesystem includes a battery or voltage source 22. The configuration shownin FIG. 6 would be used to contract or prevent/limit expansion of thehydrogel by connecting the positive terminal of the voltage source tothe implant. The negative terminal of the voltage source is connected tothe skin 26 of the patient via a patient node, which, in one embodimentis a patch 24. The current runs from the positive terminal of voltagesource 22 to core wire 28 to the hydrogel within hydrogel-containingimplant 11, through the ionic solution within the body, through patch 24and back to the negative terminal of voltage source 22.

FIG. 7 illustrates a system 20 used to augment hydrogel expansion. Inthis system the negative terminal of the voltage source is connected tohydrogel 1 via core wire 28. The current in this system would run fromthe positive terminal of the voltage source through patch 24, throughskin 26, through the ionic solution within the body, through hydrogel 1,through core wire 28 and to the negative terminal of the voltage source.

In the systems shown in FIG. 6 and FIG. 7 the wires which connect to thepositive and negative terminals of voltage source 22 may be switched tochange the polarity of the system, thus alternating between expansionand contraction of the hydrogel.

In another embodiment shown in FIG. 8 the systems shown in FIGS. 6 and 7may be combined in one system 20 utilizing two separate voltage sources.One circuit would have the configuration shown in FIG. 6 with onevoltage source, another circuit would utilize the configuration shown inFIG. 7 with another voltage source. A user could utilize a switch 32 toswitch between the two systems to either apply a positive or a negativecharge to the hydrogel. Switch 32 could be coupled to a user interface,where the user could interact with the interface to control the switchposition. In one example the positive terminal of one voltage source andthe negative terminal of the other voltage source could be connected tothe same patch.

In another embodiment, a single voltage source can utilize an H-bridgeto cause either a positive or negative charge to be applied to thehydrogel. H-bridges can be used in a circuit to vary the flow pathwithin the circuit. The circuit utilizing the H-bridge can be coupled toa user interface to control the flow path. In one position a positivecharge can be delivered to the hydrogel-containing implant, whereas inanother position a negative charge can be delivered to thehydrogel-containing implant thus resulting in either contraction orexpansion of the hydrogel. FIG. 9 illustrates an H-bridge circuitdesign.

In FIG. 9a switches 40 and 46 are closed while switches 42 and 44 remainopen. In this configuration current is delivered first through thehydrogel, through the body ionic content, through the skin patch, thenback to the voltage source. In this manner a positive charge is appliedto the hydrogel thus resulting in contraction or limited expansion ofthe hydrogel.

In FIG. 9b switches 42 and 44 are closed while switches 40 and 46 remainopen thus resulting in current flow through the skin patch, through thebody ionic content, through the hydrogel, then back to the voltagesource. In this manner a negative charge is applied to the hydrogel thusresulting in expansion of the hydrogel. An interface can be coupled tothe H-bridge circuit to allow the user to apply a positive or negativecharge to the hydrogel during the interventional procedure.

FIG. 10 illustrates the core wire-hydrogel connection. Core wire 28 canbe made of a conductive material to transfer the charge from voltagesource 22 to hydrogel 1. A separate wire may connect between theterminal of voltage source 22 and a proximal part of core wire 28 toestablish the current flow between the voltage source and core wire. Thehydrogel is connected to core wire 28 to receive the charge. Adegradable electrolytic, thermal, or mechanical linkage 30 may beconnected to core wire 28, and run between the core wire and implant 11.The linkage 30 may also be conductive in order to transfer the charge tothe hydrogel. The degradation of linkage 30 would detach implant 11 fromcore wire 28.

In another embodiment, instead of core wire 28 being conductive, one ormore wires can connect the voltage source 22 and hydrogel 1.Alternatively, wires can connect voltage source 22 to a distal part ofcore wire 28 where said distal part of core wire 28 is conductive tocarry the charge between voltage source 22 and hydrogel 1 which isattached to said distal part of core wire 28.

In an alternative embodiment an alternating current (AC) voltage sourcecan be used instead of the DC sources shown and described earlier.

Pulse width modulation or other techniques can be used to deliver thevoltage from the voltage source to the hydrogel. Pulse width modulationwould deliver voltage as a spaced waveform instead of as a constantload. Pulse width modulation could reduce potential bubbling of theionic content within the body by spacing the voltage delivered throughthe body, instead of delivering a constant load. The use of pulse-widthmodulation can be used in a combined system utilizing one or morevoltage sources. This combined system could both polarize the hydrogeland detach the implant. An example of such a system is shown in FIG. 11.FIG. 11 illustrates the outline for the system while FIGS. 11a-11cillustrate possible switch positions and how the current moves throughthe system based on the various switch positions.

FIG. 11 includes a switch 48 which either connects a portion of thecircuit (in its lower position) or a transistor 50 (in its upperposition). The transistor may provide the pulse width modulation. In theexample shown in the Figures pulse width modulation is used to polarizethe hydrogel and the direct current is used to detach the implant.However, this can be switched around if desired so that pulse-width isused to detach the implant and the direct current is used to polarizethe hydrogel. Variables such as the response of the hydrogel to electricimpulse and the material properties of linkage 30 may be useful todetermine whether direct or pulse-width modified techniques are suitablefor each purpose.

FIG. 11 a illustrates a system utilizing pulse width modulation to applya positive charge to the hydrogel. Switch 48 in its upper position sendscurrent through transistor 50, transistor 50 may alter the signal fromvoltage source 22, for example, by providing pulse width modulation. Thecurrent then travels through the hydrogel, through the ionic content ofthe body, through the skin patch, then back to the negative terminal ofthe voltage source. This flow path is due to switches 40 and 46 beingclosed.

FIG. 11b illustrates a system utilizing pulse width modulation to applya negative charge to the hydrogel. Switch 48 is in its upper positionsending current through transistor 50 which provides pulse widthmodulation. The current then travels through the skin patch, through theionic content within the body, through the hydrogel, then back to thenegative terminal of the voltage source. This flow path is due toswitches 42 and 44 being closed.

FIG. 11c illustrates a system to detach implant 11. Switch 48 is in itslower position, thus avoiding transistor 50 and providing a directcurrent via the voltage source 22. The current travels through thehydrogel-core wire interface to degrade linkage 30. A user interfacecould be coupled to the system. These figures are offered as examples ofhow a pulse-width modulation system could be used in a combined system.The pulse-width system could also be integrated into the systems shownin FIGS. 6-8. Other techniques besides the utilization of a transistorcould also be used to provide the pulse-width. In addition topulse-width, transistor 50 could also be used to provide other currentcurrent/voltage delivery options.

In another embodiment transistor 50 could be used to amplify the gainfrom the voltage source. Where transistor 50 is used to amplify the gainfrom the voltage source, this amplified gain could be used to detach theimplant. Alternatively, where transistor 50 is used to amplify the gainfrom the voltage source, the amplified gain could be used to provide anelectrical stimulus to the hydrogel to cause either expansion orcontraction of said hydrogel.

In another embodiment a transistor or other transforming mechanism couldbe used to decrease the load provided from the voltage source. Where atransistor or other transforming mechanism is used to decrease the loadfrom the voltage source, this decreased load could be used to provide anelectrical stimulus to the hydrogel to cause either expansion orcontraction of said hydrogel. Alternatively, where a transistor or othertransforming mechanism is used to decrease the load from the voltagesource, the decreased load could be used to detach the implant.

One system can be used to polarize the hydrogel and another system canbe used to detach core wire 28 from implant 11. In one example, the twosystems could utilize two separate voltage sources and have separateuser interfaces. In another example, the two systems could utilize twoseparate voltage sources and have a common user interface. Any of thesystems shown in FIGS. 6-9 could be used to polarize the hydrogel.

Alternatively, a combined system (such as the one shown in FIGS. 11, 11a-11 c) can be used to polarize the hydrogel as well as detach the corewire from the implant. This combined system would utilize the variouscircuits necessary to accomplish each task and could include a userinterface to alternate between the various systems. In one example, thiscombined system utilizes one voltage source. In one example, differentvoltages are used to either polarize the hydrogel or detach core wire 28from implant 11 via degradation of linkage 30. The user may utilize aninterface to control these voltage settings. In one example, a circuitutilizing pulse-width modulation is used to control hydrogel expansionor contraction. When detachment is desired, the user can utilize theinterface to set another setting whereby a higher voltage setting (i.e.one not utilizing pulse width modulation) would apply an appropriatevoltage to the linkage 30 and degrade the linkage from the implant.

Voltage source values can vary based on the properties of the system(i.e. the size of the implant and thus the amount of hydrogel that needsto be polarized). In one example a 9 Volt battery can be used for thesystems described above. In another example multiple 9 volt batteriescan be used in the systems described having more than one voltagesource. In another example multiple 3 Volt batteries can be used for thesystem/systems described.

Several embodiments are contemplated within the scope of this invention.

In one embodiment, an implant utilizing a hydrogel which can expandand/or contract based on interaction with electricity is described. Theimplant may utilize a carrier and a hydrogel or the implant may behydrogel alone.

In another embodiment, systems used to control hydrogel expansion and/orcontraction is described. Some of these systems are illustrated in FIGS.6-9 b. Others are described earlier within the specification. As notedearlier, these systems may be combined with other systems or combinedwith other circuitry (i.e. FIGS. 11-11 c) to perform multiple tasks,such as polarizing the hydrogel as well as initiating detachment of theimplant from the core wire.

In another embodiment, methods of controlling hydrogel expansion and/orcontraction are described. These methods involve applying an appropriatepositive charge to the hydrogel to initiate contraction (or mitigateexpansion) and applying an appropriate negative charge to the hydrogelto augment expansion. The methods of controlling hydrogel expansionand/or contraction may utilize the systems described earlier.

In another embodiment, methods of utilizing a hydrogel which undergoesexpansion and/or contraction via electricity are described. One methodmay involve using one or more of the systems described earlier to limitexpansion of the hydrogel during deployment of the hydrogel within thecatheter or delivery device. Another method may utilize the systemsdescribed above to limit expansion of the hydrogel within thevasculature until the user wants the hydrogel to expand. At this timethe positive charge may be removed and a negative charge (augmentingexpansion) may optionally be applied to enhance the space fillingpotential of the hydrogel. The hydrogel (or hydrogel-containing implant)may be detached from the core wire or delivery pusher upon placementwithin the vasculature.

In another embodiment a method of utilizing an implant comprising ahydrogel which undergoes expansion and/or contraction via electricity isdescribed. The steps described above could be utilized for an implantwhich includes a hydrogel. In an example the implants shown in FIGS. 1-2and 3-5 may be used, where the implant shown in FIGS. 1-2 allow thehydrogel to expand through the carrier and the implant shown in FIGS.3-5 does not allow the hydrogel to expand through the carrier. Thehydrogel-containing implant may be detached from the core wire ordelivery pusher upon placement within the vasculature.

Implants utilizing electrically-responsive hydrogels may also be used ina number of scenarios including but not limited to treatment ofaneurysms, atrial septal defects, patent foramen ovale, left atrialappendage occlusion, patent ductus arteriosis, fistula, arterio-venousmalformations, fallopian tube occlusion for the purposes ofsterilization, and occlusion in the peripheral vasculature. In oneexample, the expansion of hydrogel due to exposure to a negativepolarity can be used to cause a hydrogel or hydrogel-containing implantto treat any of the conditions described above. Anelectrically-responsive hydrogel could also be used as a vessel plugused to plug any of the conditions described above.

Electrically-responsive hydrogels and the systems and methods used tocontrol them could also be useful for a number of other implants andscenarios, besides the ones described earlier. This will be discussed inmore depth now.

In another embodiment an electrically-responsive hydrogel is used with adrug delivery device. In one example a drug reservoir may be placedwithin a hydrogel. When the hydrogel contracts (i.e. upon exposure to apositive charge) the drug will be released. This could be used in animplant utilizing drug delivery (i.e. an embolic coil or stent with drugdelivery). In another example the drug reservoir may sit at theperiphery of an implant and hydrogel expansion (i.e. upon exposure to anegative charge) may push the drug out, thus releasing it.

In another embodiment an electrically-responsive hydrogel could be usedwith a catheter (i.e. guide catheter, microcatheter, delivery sheaths,or other delivery devices) to aid in steering or guiding the catheterwithin the patient vasculature. A hydrogel coating could be placed atthe distal tip of the catheter, or at various locations longitudinallyalong the catheter. The hydrogel could be placed at various locationsalong the periphery of the catheter, as well. If the catheter is stuckin a particularly tortuous portion of the vasculature, the hydrogel maybe polarized (expanded or contracted) to tilt the catheter. If multiplehydrogel sections are placed along the catheter, one or more hydrogelsections can be polarized to manipulate the position of the catheterwithin the vasculature, thus aiding in tracking and navigating thecatheter. This idea could also be used to help track a guidewire withinthe patient vasculature by coating a guidewire with a hydrogel in one ormore locations and selectively expanding/contracting the one or morehydrogel portions to aid in tracking and navigating the guidewire.

In another embodiment a catheter used to deliver liquid embolic mayutilize an electrically-responsive hydrogel. Liquid embolic refluxduring liquid embolic delivery is a major issue, as the microcatheterdelivering the embolic may get stuck to the embolic mass duringdelivery. A hydrogel ring may be placed near the distal end of themicrocatheter. This hydrogel will expand upon contact with blood, butthe hydrogel can be negatively polarized to increase its expansion (orspeed up the time it takes to fully expand). In one example, uponcompletion of liquid embolic delivery the microcatheter can be withdrawnand the ring stays with the embolic mass. In another example a positivepolarity can be applied to the hydrogel to contract the hydrogel and themicrocatheter can be withdrawn along with the hydrogel. This positivepolarity can also be used to eliminate the chance of premature expansionof the hydrogel during delivery.

In another embodiment an intrasaccular occlusion device may utilize anelectrically-responsive hydrogel. An intrasaccular occlusive device maybe used to fill aneurysm or other vascular malformations. One example ofan intrasaccular device is a conformable mesh used to fill the spacewithin an aneurysm or malformation. The intrasaccular device may becoated with a hydrogel, or may have a hydrogel within the device. Thehydrogel may be coupled to a control system to polarize the hydrogel. Inone example, after placement of the intrasaccular device within themalformation the hydrogel can be negatively polarized to augmentexpansion of the hydrogel and enhance space filling potential. Inanother example, the hydrogel is positively polarized during deploymentto inhibit expansion. The positive charge can be removed (and a negativecharge may optionally be used) when hydrogel expansion is desired.

In another embodiment a stroke treatment device may utilize anelectrically-responsive hydrogel. Stroke treatment devices generallyutilize a mechanism to grasp and remove the clot or thrombus from thevasculature. In one example a hydrogel plug may be used to grasp theclot. The hydrogel plug may be positively polarized to limit expansionduring catheter tracking. Upon deployment within the vasculature, thischarge can be removed. Alternatively, a negative charge can be utilizedto augment plug expansion. The plug can be used to grasp and remove theclot. In one example, upon retention of the clot, the plug can bepositively polarized to shrink the plug and allow it to track backthrough the catheter. In another example a clot retrieval device (i.e. amechanical system used to physically grasp and remove the clot) may becoated with an electrically-responsive hydrogel to promote attachmentbetween the clot retrieval device and clot/thrombus. The hydrogel may beselectively polarized to effect contraction (i.e. during deployment) andexpansion (i.e. upon contact with thrombus).

In another embodiment an anchor within the vasculature may utilize anelectrically-responsive hydrogel. It may be desirable to anchor aguidewire within the patient vasculature to stabilize the guidewire in aparticular location. A microcatheter or delivery device can then betracked over this guidewire. A hydrogel can be used at a distal portionof the guidewire. This hydrogel can be selectively polarized. In oneexample, upon placement at the target location within the vasculaturethe guidewire is anchored into place via expanding the hydrogel (i.e. bynatural exposure to blood or via a negative polarity applied to saidhydrogel). Once the microcatheter or delivery device is tracked oversaid guidewire, the hydrogel may be positively polarized to contractsaid hydrogel and the guidewire can then be withdrawn.

The various control systems described in FIGS. 6-9 b, 11-11 c could beutilized with the various electrically-responsive hydrogel-containingdevices described earlier (i.e. drug delivery devices, steerablecatheters, liquid embolic delivery catheters, intrasaccular occlusion,stroke treatment, anchor, etc.).

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A system for electrically inducing a change instate of a hydrogel of a medical implant comprising: the medical implantcomprising the hydrogel; and a voltage source linked to the medicalimplant comprising the hydrogel; wherein the electrical current isconfigured to travel in a first direction between the voltage source andthe hydrogel of the medical implant to control contraction and/orexpansion of the hydrogel of the medical implant.
 2. The system of claim1, further comprising a patch attachable to a patient's skin.
 3. Thesystem of claim 2, wherein the patch is connected to a positive terminalof the voltage source and the hydrogel of the medical implant isconnected to a negative terminal of the voltage source.
 4. The system ofclaim 1, further comprising an H-bridge.
 5. The system of claim 4,wherein the H-bridge has a first configuration wherein the hydrogel ofthe medical implant is connected to a positive terminal of the voltagesource and a second configuration wherein the hydrogel of the medicalimplant is connected to a negative terminal of the voltage source. 6.The system of claim 4, further comprising: a switch integrated betweenthe voltage source and the H-Bridge; and a pulse width modulator; theswitch being selectively operable to connect the pulse width modulatorto the voltage source.
 7. The system of claim 6, wherein the H-Bridgehas a first configuration wherein the hydrogel of the medical implant isconnected to a positive terminal of the voltage source and a secondconfiguration wherein the hydrogel of the medical implant is connectedto a negative terminal of the voltage source.
 8. The system of claim 1,wherein the medical implant is one of a group consisting of: an emboliccoil, a drug delivery device, an intrasaccular occlusive device, and astroke treatment device.
 9. The system of claim 1, wherein the medicalimplant comprises a carrier that is distinct from the hydrogel.
 10. Thesystem of claim 9, wherein the hydrogel is secured to the carrier intension.
 11. A system for electrically inducing a change in state of ahydrogel of a medical implant comprising: the medical implant comprisingthe hydrogel; and a voltage source linked to the medical implantcomprising the hydrogel; wherein the electrical current is configured totravel in a first direction between the voltage source and the hydrogelof the medical implant to polarize the hydrogel of the medical implant.12. The system of claim 11, further comprising a patch attachable to apatient's skin.
 13. The system of claim 12, wherein the patch isconnected to a negative terminal of the voltage source and the hydrogelof the medical implant is connected to a positive terminal of thevoltage source.
 14. The system of claim 11, further comprising anH-bridge.
 15. The system of claim 14, wherein the H-bridge has a firstconfiguration wherein the hydrogel of the medical implant is connectedto a positive terminal of the voltage source and a second configurationwherein the hydrogel of the medical implant is connected to a negativeterminal of the voltage source.
 16. The system of claim 14, furthercomprising: a switch integrated between the voltage source and theH-Bridge; and a pulse width modulator; the switch being selectivelyoperable to connect the pulse width modulator to the voltage source. 17.The system of claim 16, wherein the H-Bridge has a first configurationwherein the hydrogel of the medical implant is connected to a positiveterminal of the voltage source and a second configuration wherein thehydrogel of the medical implant is connected to a negative terminal ofthe voltage source.
 18. The system of claim 11, wherein the medicalimplant is one of a group consisting of: an embolic coil, a drugdelivery device, an intrasaccular occlusive device, and a stroketreatment device.
 19. The system of claim 11, wherein the medicalimplant comprises a carrier that is distinct from the hydrogel.
 20. Thesystem of claim 19, wherein the hydrogel is secured to the carrier intension.